1

Probably not thyroid:
Even if you have an enlarged thyroid, the thyroid grows out, and it is not common for an enlarged thyroid to cause compressive symptoms. This is more likely from the reflux, or something else.
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2

Post nasal drainage:
Consider seeing an allergist or ENT or having a ct scan. Fatigue with drainage might be due to allergies or chronic low-grade infection. Also consider irrigating your nose with a sinus rinse kit by neil med. These are in virtually every pharmacy now and can help you clear secretions. Avoid antihistamines. These make infections last longer. Does food stick? You could have eosinophilic esophagitis.
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5

Itchy throat:
Please see your doc to make sure you do't have a condition that may close your throught. After that, consider getting a food sensitivity lab panel. Great Plains Laboratory in Kansas has a good one. Eliminating the offending food(s) can help. Peace and good health.
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Course varies:
The doctor was giving you a rough estimate. The time course for a cold (which is what your symptoms sound like) varies a lot from person to person and virus to virus. It's not unusual to have cold symptoms for 2-3 weeks. Generally there should be no worsening after the first 5-7 days. If high fever, severe pain, or breathing trouble develop at this point, another exam is needed.
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